with these wired in at body plug and everything on the rb25 connected such as afm cas etc it will start and run but if you want to wire it in properly here is a short run down.

Alternator, Starter, Etc.:
The easiest way to wire the driver’s side loom is to graft the RB30 loom onto the 25.
Undo all the wires off the RB25 alternator, starter and oil pressure sender.
• Remove all the tape and conduit shielding from the loom and separate the knock sensor wiring from the rest.
• The knock sensors are the two sensors at the top of the block under the intake plenum.
• Remove the RB25 alternator and bolt on the RB30 one.
• Unplug the RB30's driver’s side loom from the car (or RB30 if you kept it attached) and attach it to the RB25's knock sensor wiring. Plug in the alternator and starter motor. You can use the RB25 starter with the RB30 wiring no worries.
• Remove the RB30 oil pressure sender unit from the RB30 block and screw it in place of the one on the RB25. Plug it into the RB30 loom now on the RB25.
• Cover the loom with the conduit wrapping and electrical tape to neaten it up.
• Grab the main earth wire off the RB30 block and put it in place of the one from the RB25.

Fuel Pump
The fuel pump in an R33 is earthed through the ECU.
Series 1 loom
in the foot well plug (long white one ON THE ENGINE LOOM NOT THE CARS DASH\BODY LOOM)
thin white/black - constant 12v
thickish red - ign 12v through a pair of 6A diodes (or one big one making sure the silver bands face the way u want the current to flow) to stop voltage flowing backwards to ground. If you don't use diodes the ignition won't turn off.

Black/red - ign 12v
yellow/blue - tacho, using the pull up circuit already detailed.
Light blue/white - ign 12v, it’s for the vct and 02 sensor
black/purple - fuel pump relay control
Dark blue/black - temp gauge
grey/red - 12v under cranking
There are only two wires needed to make the Engine start now. One needs constant power and the other needs ignition power.
• ECU plugs white wire with black trace. Tap the constant power in to it.
• Thick black wire with red trace (BR). Tap ignition power into this wire.
Now if your fuel pump primes and shuts off after a few seconds you've done it correctly. At this stage the engine should run if everything else is done.

Tachometer
• Find tacho signal wire from the dash plug.
• Coming out of pin 7 on the ECU is a yellow wire with red trace (YR). This is the tacho signal to the ECU. You could splice a wire into this but I'd advice looking in the engine bay and finding a small rounded plug on the afm branch by the passenger strut tower. It has a single wire going into it and a rubber cap on the end. The wire is yellow with blue trace (YL). This is also RPM signal. Attach to tacho signal wire.
• Now you'll need to go grab a 10k resistor. You'll need to splice a wire into wire 49 from the ECU, run it through your resistor, and finally splice it into the tacho signal wire.

On the rb25 loom about 20cm from the ecu is a 10cm long white body plug in that is the coloured wires i described that need connecting to the vl body loom under the a/c there is several green wires one is for the fuel pump trigger , pink wires that are switch power and for constant power i ran a new wire

To find the correct green wire on the blue plug under a/c, the green wire next to the orange with no strip is fuel pump signal

Nice! cheers for that image of the plugs, the rb30det.info link doesnt work for me tho for some reason.

Only thing I'm having trouble with now is the alternator wiring I can swap the plugs over easy enough, but im using the rb30 drivers side loom with the rb25 alternator so I was wondering if the leads that go to the bacxk of the alternator will bolt on?

---------- Post added 27-08-13 at 14:55 ----------

Actually yea I can't see the writing on the image because its too small, and the link gives an internal error :/

Top row blue is oil pressure i used the rb30 sensor and also ran the wire through the engine loom to the body connector

Top row right brown/red is tacho connect to the yellow red strip with a pull up resistor

Pink wire i used as switch power for the fat black red strip in rb25 body connect
2nd Pink wire i used as switcd power for the light blue white strip in rb25 body connect this is for vct , o2 sensor, afm power

I ran a new constant power to the thin black white strip which runs to the ecu relay

The solid black are all earths which i put on an eye let then screwed to clean matal somewhere near ecu.

It will start without it, but is a bitch when cold.
The purple wire that is in the factory vl loom that runs to your starter motor. Which is the same one used for the factory auto neutral start relays, which you bridge when you do a manual conversion.

The link I posted is to the r31skyline site, so naturally the wiring colours won't be the same as a VL's wiring...

I presume you mean on either the blue or purple underdash plug in the VL? The blue with white stripe is the starter signal wire that goes from the 2 pin plug on the starter to the ecu and the fat orange one is just constant 12v. If you are using a skyline starter the wire will most likely be a different colour

Don't forget to swap the single pin coolant temp sender to a VL one so the dash will read correctly

Top row blue is oil pressure i used the rb30 sensor and also ran the wire through the engine loom to the body connector

Top row right brown/red is tacho connect to the yellow red strip with a pull up resistor

Pink wire i used as switch power for the fat black red strip in rb25 body connect
2nd Pink wire i used as switcd power for the light blue white strip in rb25 body connect this is for vct , o2 sensor, afm power

I ran a new constant power to the thin black white strip which runs to the ecu relay

The solid black are all earths which i put on an eye let then screwed to clean matal somewhere near ecu.

"I ran a new constant power to the thin black white strip which runs to the ecu relay"

How do I tell which one of the white/black wires to connect into? They all look the same in the back of the blue ecu relay

The plug on the vl starter will have a white and a blue/white wire going into it. The white goes to the alternator and the blue/white is your cranking signal. Those 2 wires also go through the 4 pin grey plus which has the 4mm wires in it as well from memory.

There should be a spare plug on the 25 loom that has all the power source wires in it. Trace which one you need to tap into at the relay with a multimeter. Do the relay pins have numbers on them? It's been a while since I've looked closely at a skyline loom

Red cable goes to the battery lug on the starter, brown goes to the battery light in your dash, white goes to the starter also and it may also have an earth strap on it which just goes to the block. They are the VL colours but you should be able to work out which is the dash wire (brown vl) and which is the sense wire (white vl) as the plug is the same depending on your RB30 alternator type

I already hooked up a red cable to the starter and theres another one so I thought it had to go to the alternator. I believe im running a vl alternator as it says bosch 70 amp on the side of the rear black cover. If i have the 30 alt it earths through the mount on the block and i dont need to run an extra earth right?